I have a crate motor from ford racing 302 with E cam and aluminum X heads.BBK SSi intake with 65 MM TB.At the moment I have stock fuel pump and 24 LB injectors with Anderson MAF along with adjustable BBK FPR wit 1:1 boost ratio.
The SN89 is unmolested and in great condition
I made my own harness from my stock f150 SD one rewired for SEFI and MAF and remote mouted TFI on heat sink mounted to inside fenderwell.All connections are direct I removed all the plug connections I could and soldered everything and heat shrinked all connections.
Truck fires right up and goes through cold idle then starts to surge from 1500 rpm's to 200 cycles 3-5 times then stalls.. TPS voltage set and Fuel pressure is at 40 or so pounds had to adjust with surge.Vaccum is a solid 12-15 on meter.
My IAC is from old motor and worked fine when on this motor.If I unplug it truck dies so I guess its working.All voltages at MAF and BAP check out good.
Not sure if I should get computer flashed in a closed loop configuration to see if this helps?My O2's are new also..
I have been toooo trifty on this build though and purchased alot of used parts that I was told were in working order. IE the EEC MAF injectors motor and supercharger..
Like I said it starts right up and idles high for 30 secs or so then starts nasty cycle of surging up and down till stalls.
Your idle should hold with the IAC unplugged. Set the idle screw on the throttle body then plug the IAC back in after removing the battery power for a couple of minutes to reset the memory saved setting. Your IAC is trying to correct for a vacuum leak or it is working out of range because of the throttle blade position reading from the TPS.
Get a hand vacuum pump and switch it to pressure and pump it up and listen for leaks. It is really easy to hear them when the engine is not running. To be honest 12-15 vacuum seems really low. I would expect close to 20 vacuum with a E cam.
I unplugged the IAC and spout today and set the TB screw so truck would Idle around 1k RPM's. It stayed running for as long as I wanted it to. If I did crack the throttle a bit IE 3Krpms or so it would come back down and Idle at 1K RPM's just fine.
When I plugged IAC back in it would surge and stall.
I also was able to unplug the FPR vacuum line and stick finger on the end with very good suction on my finger tip I then set FPR so my gauge read 38PSI.
I do believe it is running pretty rich as there was soot on the ground behind tailpipes. It is pretty cold here in NH though 30's today. Another thing noticed was the drivers side tailpipe was exhausting more vapors than the passenger side.(you know when its cold outside and your exhaust has a bit of smoke, Similar to when you breath out in the cold)
I will quaddroople check for vacuum leaks tomorrow.Can I just pressureize it with my air compressor ?I would think it would just escape through TB though?One other thing I did do was pull the Vacuum line off brake booster.I heard a good woosh sound when air escaped..
Lower your FPR to get idle a little leaner. I would start at 28-32psi which is normal. With it running and the IAC unplugged get a vacuum reading. Is the reading steady. Next while the car is running unplug the MAF. What Happens?
You can make a boost pipe. This is what the turbo guys like my son uses on his Talon to test for boost and vacuum leaks. You make one by taking PVC pipe end plug and drill and install a tire valve. Take the pipe with a pipe clamp and install it on the throttle body and pressurize the engine with 10psi of air and start listening for your leak. This is the best thing that Dodge/Mitsu ever designed to test for boost leaks.
If I keep giving all my secrets away I will be out of business...lol
Do I need to run a IAC? I was reading about a IAC bypass? Whats you thoughts?
something I read
Quoted from another site.
99% of the time on a cammed car opening up the divider between the ports on the IAC with a dremel so the motor idles at 1000rpm with the IAC unhooked, the throttle plate shut and the TPS at .98vdc fixes all surge related problems. Found about to do that on my '93 with a very mild cam and good induction it didn't like idling below 900rpm. The IAC can't react quick enough to a lopey cam induced RPM fluctuation so instead of dampening the surge it increases it. Every E cammed car I've ever worked on needed this to keep a stable idle. Similiar to Fords idle bypass plate without the cobbled look.
I have not seen this to be honest, the E cam is a Emission cam so it most idle at stock and not effect the engine management. To not effect engine management it must supply stock vacuum at idle and up to 2500 rpm which is the Emission rolling tail pipe test. I myself would make a block off plate and not use the IAC for a cleaner look unless you have air condition and the motor won't hold idle with the air on.
Just block it off. All the IAC does is open the path for a vacuum leak to control idle. You could even have the problem your having if the motor is bad or the unit has a bunch of carbon in it. Just leave the connector unplugged.
Just a quick note on the E cam... I had one in my last 5.0, and despite being emissions legal, my A9P computer didn't care for it much. It would idle well once it was warmed up, but if I started it cold and just let it idle, it would start surging until it would die. I did have 1.7 rockers which effectively increased the cam profile a bit.
Actually I just remembered I "solved" the problem by disconnecting the IAC and setting the idle where I wanted it. It did idle a bit low when cold in the mornings, but it beat the hell out of trying to get the IAC to work right.
Just never had a problem with this Alphabet Cam. Now the 'F' cam got that letter for a reason. lol
Always needed a tuner device to fix the idle with that puppy.
Reply With Quote
Bookmarks